Bag for packaging bone-in cuts of meat

ABSTRACT

Disclosed is a bag arrangement and packaging method for packaging bone-in cuts of meat using two bags to provide a double wall of film surrounding the cut of meat for bone puncture resistance. Both bags are bottom sealed bags formed of a heat shrink film, the inner bag has an interrupted bottom seal to provide an opening for venting air between the bags and the outer bag has a continuous bottom seal. The outer bag is longer than the inner bag so the outer bag can be closed without involving any portion of the inner bag in the closure. The bone-in cut of meat is inserted first into the first bag and then the first bag and its contents are inserted into the second bag, the bags are evacuated and then the outer bag is closed.

TECHNICAL FIELD

The present invention relates to the packaging of bone-in cuts of meatand more particularly to a method and means for packaging such meat cutsin a heat shrink bag arrangement which decreases the likelihood of abone puncturing through the bag.

BACKGROUND OF THE INVENTION

The use of bags formed of a heat-shrinkable thermoplastic film forpackaging primal and sub-primal cuts of meat is well known in the art.In use, the cut of meat is loaded into the bag. The bag is evacuated toremove air so the bag collapses against the cut of meat and then it isheat sealed to maintain the evacuation. Next the bag is exposed to warmwater at about 90° C. or other heating means causing the bag to shrinkand form fit the cut of meat. Packaging in this fashion excludes airfrom the package to prolong shelf life and reduces weight loss due todrying of the meat.

The bag film is relatively thin and usually not more than about 3 to 4mils (0.076 to 0.10 mm) thick. Accordingly, these bags generally are notsuitable for packaging cuts of meat which contain bones. For example,the ribs or other sharp bone protrusions as contained by rib beef cutsor pork loins and other meat cuts may puncture the bag during theevacuation of air or during heat shrinking as the bag draws tightlyabout the bone-in meat cut. Any puncture in the bag is undesirable as itallows the meat cut in the bag and especially in the area of thepuncture to be exposed to the air. The puncture also is a possiblesource of contamination. The problem of bone punctures is compounded byabrasion during movement of the package along a conveyer and as it isloaded into corrugated boxes and by abrasion between adjacent packagescaused by vibration and movement of the meat packages one againstanother during transport and handling.

One technique for preventing bone puncture is to overlay the protrudingbones of the cut of meat with paper, cloth or a wax impregnated clothprior to insertion into the bag. This is shown for example in U.S. Pat.Nos. 2,891,870 and 4,136,205. Another common solution is to improve thepuncture and abrasion resistance of the bag film by adhering a patch tothe outer surface of the heat-shrinkable bag. U.S. Pat. No. 4,755,403discloses use of an oriented heat-shrinkable patch affixed by anadhesive to the surface of a heat-shrinkable bag and U.S. Pat. No.5,302,402 discloses a non oriented patch adhered to the bag surface bycorona treatment. In order to provide the bag with greater protection,U.S. Pat. No. 5,545,419 discloses adhering two heat shrinkable patchesto the bag, one to each outer surface of the flattened bag. The patcheseven may extend over the side edges to insure that coverage extends thefull width of the bag.

Neither the cloth nor paper overlay nor a patch adhered to the outersurface of the bag are entirely acceptable solutions to the problem ofpreventing bone punctures and providing abrasion resistance. One reasonfor this is that the overlay may be dislocated from its laid-on positionas the bone-in cut of meat is inserted into a bag. Patch-bags with onepatch require some manipulation of the heavy cut of meat to insure thatthe patch is properly oriented over the protruding bones. Anotherdrawback of patch bags is the cost of manufacturing the patch materialand the added cost of having to laminate one or more patches to the bag.Also, the patch material generally is thicker than the bag. As a resultthe patch bag tends to be relatively stiff due to its thickness and thisstiffness further adds to the difficulty of handling the bag during apackaging operation.

Attempts to avoid applying a patch to the bag have includedmanufacturing the bag with multiple plies along one side to provide bonepuncture resistance. For example U.S. Pat. No. 4,704,101 and 5,020,922disclose heat sealing a wide area of a laid flat tubing to itself toform a double thickness, corona treating one flattened side and thenfolding the tubing so that the double thickness overlays one of theflatted sides. This forms a triple ply along one side of the bag and asingle ply along an opposite side wherein all the adjacent surfaces ofthe three ply side are interfacially bonded. U.S. Pat. No. 4,481,669discloses inserting a narrow longitudinally folded web into a widerlongitudinally folded web and then heat sealing across the webs to formside sealed bags which have a single thickness adjacent the bag mouthwhile the rest of the bag has a double thickness. Further, the webs arecorona treated so that the plies of the bag adhere one to the other. Itis believed that due to the complex nature of the manufacturing process,neither of these bags has a commercial embodiment.

Accordingly, it is an object of the present invention to provide animproved heat shrinkable bag structure and method for packaging bone-incuts of meat.

Another object of the present invention is to provide a bag forpackaging bone-in cuts of meat that has a wall structure which is twoplies thick for bone puncture resistance.

A further object is to provide a bag structure for packaging bone-incuts of meat which locates a double thickness of bag film around theentire cut of meat for puncture resistance and yet has only a singlethickness in the region of the bag closure.

Still further object is to provide a bag-in-a-bag structure forpackaging bone-in meat cuts wherein the inner bag includes at least oneopening remote from the bag mouth to facilitate evacuation of air frombetween the bags.

Yet another object of the present invention is to provide an improvedmethod for packaging bone-in cuts of meat wherein double-bagging is usedto provide bone puncture resistance.

SUMMARY OF THE INVENTION

The present invention involves the use of two individual bottom sealedbags to package a bone-in cut of meat. Bottom sealed bags are made bylaying a tubular film flat and then making transverse heat seals acrossthe bag width at spaced intervals to weld the flattened sides of thetube together. The tube is severed at the same time it is heat sealed.This forms a so called "bottom sealed" bag which, when it is laid flat,has a bottom edge formed by the heat seal, an open mouth formed by thesevered edge and two seamless side edges formed by the fold producedwhen the tube is laid flat.

The two bottom sealed bags according to the present invention are to bedisposed one within the other. These two bags are slightly different inconstruction. A first bag, to be used as the inner bag, is shorter thanthe other. The open end of the inner bag should be more blunt ascompared to the open end of the other bag for reasons set outhereinbelow. Also, its bottom seal is interrupted or not complete allthe way across the bag width to provide a passage for venting air fromone bag to the other. A second bag, to be used as the outer bag, islonger than the first bag and its bottom seal is continuous across thebag width. Other differences are further set out hereinbelow.

The bags can be made of different films to provide different properties.For example, the outer bag can be a film structure having oxygen andmoisture barrier layers while the inner bag is a non barrier film. Atleast the outer bag and preferably both bags are formed of a heatshrinkable film. For purposes of the present invention, the term "heatshrinkable" means that the film used in making the bags is biaxiallyoriented such that it has an unrestrained shrink of at least 10% andpreferably at least 30 to 40% shrink or more in each of the transverseand machine directions measured at 90° C. Free shrink is measured bycutting a square piece of film measuring 10 cm in each of the machineand transverse directions. The film is immersed in water at 90° C. forfive seconds. After removal from the water the piece is measured and thedifference from the original dimension is multiplied by ten to obtainthe percentage of shrink. It also is preferred that both bags be madefrom the same film to avoid the need for different film extrusion lines.

A suitable film is a multilayer film having a barrier layer disposedbetween a heat sealing layer and an abuse layer. The inner or heat seallayer is a blend of four polymers including:

a) a first polymer, and specifically Mitsui Petrochemical IndustriesTAFMER® A0585x which is a C₂ -C₄ copolymer having a density of 0.885g/cm³ melt index (MI) of 0.5 dg/mm, a melting point (MP) of 68° C.,which is referred to herein as "Plastomer";

b) a second polymer such as a Dow Chemical Company AFFINITY® PL1880which is an ethylene-octene copolymer having a density of about 0.902g/cm³, a MI of about 1.0 dg/min. and an MP of about 100° C. Dow'sAFFINITY resins are made using constrained geometry catalysts which, arereferred to herein as metallocene very low density polyethylene(mVLDPE);

c) a third polymer such as Dow's ATTANE® XU 61509.32 which is anethylene-octene copolymer having a density of about 0.912 g/cm³, a MI ofabout 0.5 dg/min., an MP of about 122° C. and a Vicat Softening Point of95° C., which is referred to herein as VLDPE.

d) a fourth polymer and such as an Exxon Chemical Company LD 701.06 EVAhaving a vinyl acetate content of 10.5%, a density of 0.93 g/cm, a MI of0.19 dg/min. and an MP of about 97° C.

The film core or barrier layer is any suitable barrier material such asvinylidene chloride-methacrylate (VDC-MA) copolymer or a vinylidenechloride-vinyl chloride (VDC-VC) copolymer or a blend of barriermaterials.

The outer abuse layer of the film was formulated of a blend of:

a) the first polymer (Plastomer) such as a Mitsui Tafmer A 0585X;

b) the second polymer (mVLDPE) such as a Dow AFFINITY PL1880; and

c) the fourth polymer (EVA) such as an Exxon LD 701.06.

A suitable blend for the heat seal layer is about 24 wt. % of thePlastomer, about 29 wt. % of the mVLDPE, about 19 wt. % of the VLDPE andabout 19 wt. % of the EVA with the balance being slip aids andstabilizers.

A suitable blend for the abuse layer is about 24 wt. % of the Plastomer,47 wt. % of the mVLDPE and about 24 wt. % of the EVA with the balancebeing processing aids.

The inner and outer bags can be made with the same bag making equipmentmerely by changing the heat sealing assembly. One assembly would have ashape to form the continuous heat seat bottom edge of the outer bag. Thesecond assembly would have a shape to form the interrupted heat seat ofthe inner bag. In fact, if desired, the same heat sealer could be usedto make both bags. The only change needed in this case is to mask off ashort section of the heat sealer to make the interrupted seal of theinner bag. If desired, the inner bag can be slightly narrower than theouter bag to facilitate the insertion of the inner bag into the outer.However having different width bags is not essential. It is preferred,however, that the inner bag be shorter than the outer. This allowsclosing the bag by heat sealing through only the film thickness of onebag as is conventional, rather than through the double thickness of twobags.

In the method of the present invention, the bone-in cut of meat isdouble bagged. The operator first puts the bone-in cut of meat into theinner bag. The inner bag then is put into the outer bag. The bags areevacuated in a conventional manner which draws air from the inner andouter bags. The interrupted seal of the inner bag allows communicationof the air spaces between the bags to insure that air is evacuated fromboth bags and from between the bags. Next the outer bag is closed in aconventional manner to maintain evacuated conditions. Since the innerbag is shorter than the outer bag, closing the outer bag involves onlythe single film thickness of the outer bag. This is particularlyimportant when using a heat sealer to close the bag as it is easier toheat seal through two film plies than through four.

Accordingly, the present invention may be characterized in one aspectthereof by a double wall bag comprising a pair of heat shrinkable bottomsealed bags placed one within the other. The outer bag is has acontinuous heat seal extending across the bag width which forms theclosed bottom of the outer bag. The inner bag is shorter in length thanthe outer bag and has an interrupted heat seal extending across the bagflat width forming the bottom of the inner bag. The interrupted sealdefines an opening that permits the passage of air between the two bags.

In another aspect, the present invention may be characterized by amethod for packaging bone-in cuts of meat comprising:

a) inserting a bone-in cut of meat into the open end of a first bottomsealed bag formed of a heat shrinkable film, the heat seal forming thebottom of the bag having at least one opening which provides access tothe interior of the bag;

b) inserting the first bag and the bone-in meat cut it contains into asecond bottom sealed bag formed of a heat shrinkable film, the secondbag having a length greater than the first bag;

c) evacuating air from the first and second bags by communicating thesecond bag to a source of vacuum wherein the opening in the bottom sealof the first bag allows the passage of air from one bag to the other;

d) closing the second bag by forming an air tight closure from the extralength of bag film without involving any portion of the first bag insaid closure; and

e) exposing the evacuated package to heat shrinking temperatures to heatshrink at least the second bag thereby forming an article comprising abone-in cut of meat in an evacuated double walled heat shrunk filmpackage.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing the double bag structure of thepresent invention; and

FIGS. 2-5 illustrate steps in a packaging method using the bag of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings, FIG. 1 shows the double bag structure of thepresent invention generally indicated at 10. The double bag structureincludes a first bag 12 which is the inner bag, and a second bag 14which is the outer bag. At least the outer bag 14 is made of a heatshrinkable film and preferably, both bags are heat shrinkable.

While both bags may be made of the same film, it is preferred that atleast the outer bag 14 comprises a barrier film. A "barrier" or "barrierlayer" means a layer of a multilayer film which acts as a physicalbarrier to oxygen and moisture. The barrier layer will reduce the oxygenpermeability of the film used to make the bags to less than 70 cc persquare meter in 24 hours at one atmosphere at 23° C. and 0% relativehumidity. These values should be measured in accordance with ASTMstandard D-1434.

The inner bag 12 may be a side sealed bag and the outer bag 14 a bottomsealed bag. However, it is preferred that both bags are bottom sealedbags. As noted above, a bottom sealed bag is formed from tube stock. Thetube is collapsed so it lays flat and a heat seal is made across thetube to form the closed bottom edge of the bag. The side edges of abottom sealed bag are seamless in that the side edges of the bag aremerely folds in the laid flat tubing. Bottom sealed bags aredistinguished from side sealed bags. The latter are formed by folding aweb and applying two spaced heat seals across the folded web such thatthe fold forms the bottom of the bag and the two spaced heat seals formthe side edges of the bag.

Accordingly, first bag 12 has seamless side edges 16 and a bottom edge18. defined by a heat seal formed by heat sealing the flattened sides oftubular film together. As shown in FIG. 1, the first bag has a ventopening 20 which is spaced from the open end 32 of the bag. Preferablythe vent opening is provided in the heat seal that defines the bottomedge 18 of the bag. In this respect, the heat seal is not continuous.Instead, the seal is interrupted to provide the vent opening 20. Whileone opening is shown, several openings may be provided along the lengthof the seal. If the inner bag is a side sealed bag, then the opening 20is provided either in one or both side seals or is cut in the foldedbottom of the bag. In any event it is preferred that the vent opening bespaced from the open end of the bag as shown so that the opening islocated adjacent the bottom of the bag.

The second bag 14 is conventional in that it has seamless side edges 22and a bottom edge 24 formed by a continuous heat seal. Also, forpurposes of the present invention, it is important that the second bagbe longer than the first bag, the extra length being indicated at 26.

The heat seal forming the bottom edge of each bag may extend straightacross the bag. It is preferred, however, that the heat seal be arcuatesuch that the bottoms of both bags are convex. This convex shapeprovides a better fit with the cut of meat inserted into the bag and abetter appearing package after heat shrinking. In making bottom sealedbags, the same arc shape for the heat seal is followed to cut off thebag so that the open end of the bag is concave.

Referring to the shape of the second bag 14, FIG. 1 shows that theconcave shape at the bag open end 28 produces "ears" 30 which bracketthe open end. Similar ears are not desired at the open 32 of the firstbag for reasons set out hereinbelow. Accordingly, it is preferred thatthe arc shape forming the bottom edge 18 of the first bag be shallowerthan that of the second bag. This produces a less concave shape for theopen end 32 of the first bag and reduces the prominence of the resultingears 34.

Reference is made to FIGS. 2-5 which illustrate a method of packaging abone-in meat cut according to the present invention. FIG. 2 shows that abone-in cut of meat 35 is inserted into the first bag 12. Depending uponhow close the bag is fitted to the size of the meat cut, some air may beexpelled through the opening 20 in or adjacent the bottom seal of thebag. Next the first bag is inserted into the second bag 14 (FIG. 3). Thefirst bag is pushed deep into the second bag so that the excess length26 of the second bag extends beyond the open end 32 of the first bag.

FIG. 3 further illustrates the potential air flow paths during asubsequent evacuation step. In this respect when air is evacuated fromthe outer bag, air flows out from the open end 32 of the inner bag 12 asindicated by arrow 38. Air also is drawn from between the first (inner)bag 12 and the second (outer) bag 14 as indicated by arrows 40. Theopening 20 in the bottom seal of the inner bag 12 allows for the passageof air through the opening as indicated by arrow 42 to insure theevacuation of air from any space 44 behind the bone-in meat cut 35.

The evacuation of air in effect collapses both bags against the bone-incut of meat as shown in FIG. 4. The open end 28 of the outer bag then isclosed by any suitable means (not shown) such as by gathering andclipping or by heat sealing across the flat width of the bag. Thismaintains the evacuation of the bags.

Since the outer bag is longer than the inner, gathering and closing theouter bag 14 can be accomplished using only the two plies of the outerbag contained in the extra length 26 and without involving any portionof the inner bag 12. Also, the less prominent ears 34 (FIG. 1) at theopen end 32 of the inner bag are less likely to extend into the area ofthe closure. This is especially important when the closing isaccomplished using a heat sealer. Less energy is required to heat sealtwo plies than to heat seal three or four plies and a more reliable andconsistent heat seal closure is made if the same thickness of film isused.

Simultaneous with the closing of the bag, at least a some of the extralength 28 may be trimmed to form the evacuated and sealed bone-in meatpackage 48 as illustrated in FIG. 5. The next step in the packagingprocess is to expose the bone-in meat package 48 to 90° C. water orother heating means to shrink the film comprising the inner and outerbags.

The double bag structure as described hereinabove provides severaladvantages over prior art arrangements for packaging bone-in cuts ofmeat. For example, the puncture resistance provided by double baggingthe cut of meat extends completely around the entire cut of meat with nointerruption. This was not the case even with patch bags of the priorart that have patches on both sides of a bag or patches extending overthe edges of the bag. There is an ease of use in that the meat cut neednot be placed in the bag in any particular orientation in order to coverthe protruding bones with an extra thickness of film. There is no needfor special manufacturing equipment to fold, corona treat or make broadheat seals in order to make a bag having a thicker wall along one sideof the bag. Laminators and adhesive applicators for adhering a separatepatch film to a bag film also are avoided.

Use of the double bag arrangement of the present invention further isfacilitated by the design of each of the two bags. In particular, themeat cut 35, when it is inserted into the first (inner) bag 12 can seatagainst the partially closed bottom 18 of the bag. This is important incertain bagging operations wherein pushing a cut of meat into a bagforces the bag off of a bag holder. The interrupted heat seal formingthe closed bottom 18 of the first bag provides a vent opening 20 whichallows the venting of air from the rear of the inner bag duringevacuation. Having the first bag which is shorter in length than thesecond (outer) bag avoids having to include film material of the firstbag in the closing of the second bag after evacuation.

Thus it should be appreciated that the present invention accomplishesits intended objects in providing an improved bag arrangement and methodfor the packaging of bone-in cuts of meat. The present inventionprovides a bag having a double thickness extending around the entire cutof meat while providing only a single thickness for closing the openmouth of the bag. The double thickness further is provided without theneed to laminate patches or to have special manufacturing equipment formaking bags having an unbalanced wall structure. Providing an opening inthe bottom of the inner bag further insures proper venting of air fromthe inner bag.

Having described the invention in detail, what is claimed as new is: 1.A double bag structure formed of two individual bags for packagingbone-in cuts of meat comprising:a) a first heat shrinkable and heatsealable bag having a bottom end defined by a heat seal extending acrossthe bag and an open end for directly receiving a bone-in cut of meat,said first bag having a vent opening through said heat seal at saidbottom end; b) a second heat shrinkable and heat sealable bag having aclosed bottom end defined by a heat seal extending across the bagwithout interruption and an open end for receiving said first bag andits contents, said second bag being longer than said first bag by anamount sufficient to permit the heat sealing of the second bag open endwithout the involvement of any portion of said first bag in suchsealing; and c) at least said second bag being formed of a barrier film.2. A double bag structure as in claim 1 wherein first bag is a bottomsealed bag and said vent opening is defined by an interruption in saidheat seal forming the bottom of said first bag.
 3. A double bagstructure as in claim 1 wherein both said first and second bags are eachformed of a multilayer heat shrinkable barrier film.
 4. A double bagstructure as in claim 1 wherein:a) both said bags are bottom sealed bagsand have a bottom formed by a heat seal that extends in an arc across aflat width of each of said bags; b) said heat seal forming the bottom ofsaid first bag being interrupted along its length and said interruptiondefining said vent opening; c) said heat seal forming the bottom of saidsecond bag being continuous and uninterrupted; and d) said heat sealforming the bottom of said first bag being shallower and less convexthan the heat seal forming the bottom of said second bag.
 5. A doublebag structure as in claim 1 wherein said length difference between saidbags is sufficient to permit the forming of a closure for said secondbag without involving any portion of said first bag in the forming ofsaid closure.
 6. A double bag structure as in claim 1 wherein each bagis formed of a multilayer film comprising:a) a heat seal layer being ablend of Plastomer, a first very low density polyethylene, a second verylow density polyethylene made using a constrained geometry catalyst, andethyl vinyl acetate; b) an abuse layer being a blend of Plastomer, avery low density polyethylene made using a constrained geometrycatalyst, and ethylene vinyl acetate; and c) a barrier layer betweensaid heat seal and abuse layers.
 7. A double bag structure for packagingbone-in cuts of meat comprising:a) a pair of independent bags eachformed of a heat shrinkable and heat sealable film including a first bagfor directly receiving a bone-in cut of meat to be packaged and a secondbag for receiving said first bag and its contents, said bags beingbottom sealed bags wherein an arcuate transverse heat seal forms eachbag with a convex bottom; b) said arcuate heat seal forming the convexbottom of said first bag being shallower and less convex than thearcuate seal forming the convex bottom of said second bag and beinginterrupted along its length to provide a vent opening through thebottom of said first bag; c) said arcuate heat seal forming the convexbottom of said second bag being continuous and uninterrupted along itslength; d) said second bag being longer than said first bag and thedifference in the length of said bags providing said second bag with asufficient film length to form a bag closure for said second bag by heatsealing without involving any portion of said first bag; and e) at leastsaid second bag being formed of a barrier film.